The invention relates to a machine for producing a knitted fabric from fibre material, in particular a circular knitting machine.
Machines of this type are distinguished by the predominant or exclusive use of threads that consist of largely untwisted staple fibres arranged parallel to one another instead of classic yarns. Such threads are produced in drafting devices connected directly in front of the stitch-forming points of the machine from slivers or bands fed to them, and to ensure a disturbance-free transport from the drafting devices to the stitch-forming points, are converted by means of spinning elements into temporary yarns, the twists of which are only removed again shortly before running into the stitch-forming points (false twist effect). Therefore, the threads actually processed into knitted fabric substantially consist of untwisted parallel threads, which is why the finished knitted fabric is distinguished by an extreme softness. While additional auxiliary threads consisting of classic yarns can be worked in, if required, this is not fundamentally necessary.
A known machine of the aforementioned type configured as a circular knitting machine (PCT WO 2004/079068 A2) has one drafting device for each stitch-forming point. Since the drafting devices cannot be configured as small as desired, a substantial space and handling problem results. Therefore, it has been provided, for example, to arrange the drafting devices at comparatively substantial distances from the circular knitting machine and to surround this with a raised work platform, from which the drafting devices are accessible. While it is possible as a result of this to arrange a large number of drafting devices on the periphery of the circular knitting machine, this poses the disadvantage that when a fault occurs in one of the drafting devices, the operator working on the circular knitting machine must leave his/her usual work area in front of the machine, get on the work platform, eliminate the fault from there and than return to his/her usual work area. This is not only inconvenient, but also requires special cost-incurring protective measures in the form of railings or the like that delimit the work platform in order to prevent the operator from accidentally falling from the work platform. Moreover, additional measures that further increase the production costs must be taken, which consist, for example, of a multiplicity of spinning elements and transport tubes following these for each stitch-forming point in order to securely transport the threads leaving the drafting devices as far as the knitting needles or other stitch-forming elements. If in order to avoid these disadvantages the drafting devices were arranged directly on the machine, in particular on the periphery of a circular knitting machine, then the space between the drafting devices would become ever smaller as the number of knitting points or systems increases, so that with the usual arrangement the drafting devices would no longer be accessible and economic maintenance operations and/or repairs of the drafting devices would thus be practically impossible.
In addition, it is also already known to combine the drafting devices in a bar shape to form three groups, which are arranged at angular distances of approximately 120° on the periphery of the circular knitting machine. However, this solution poses the additional advantage that the routes of the drafting devices to the stitch-forming points fluctuate greatly. This results in different friction conditions for the threads, in particular if transport tubes are also used in this case, which can result in different thread tensions and cause the threads exposed to an increased friction to break more easily. Apart from this, all solutions, in which two or more spinning elements operated mechanically or by compressed air are necessary for each stitch-forming point, have the disadvantage of increased energy consumption.